The present invention relates to overhead conveyer systems for the movement of hanging products. In particular, the invention relates to pusher dog assemblies designed for the transportation of hanging products in an overhead conveyer system.
Overhead conveyer systems are well known in the present state of the art. The systems are used for transporting various types of merchandise, including hanging garments and other products, through manufacturing, warehousing and distribution facilities. Typical overhead conveyer systems are xe2x80x9cpower and freexe2x80x9d systems that push heavy, metal trolleys along a track system. The trolleys carry loads of products, such as garments on hangers (xe2x80x9cGOHxe2x80x9d).
Power and free conveyer systems employ a system of two, parallel tracks; an upper power track and a lower free track are incorporated. The upper track generally includes a drive chain that engages a component of the trolley, while the trolley""s wheels are designed to ride within the free track. The load supported by the trolley (e.g., GOH) is most often suspended below the level of the free track. The drive chain commonly includes a pusher dog that extends downward from the drive chain and engages a part of the trolley that protrudes above the level of the free track. A pusher dog is, generally, a projection that engages and pushes loads along a track or conveyer system. Movement of the trolley is thus accomplished by the mechanized action of the pusher dog on the protruding trolley part
There are many instances of power and free conveyer systems in the present state of the art, including several references to pusher dogs. U.S. Pat. No. 6,367,612 to Dosso et al., U.S. Pat. No. 6,308,637 to Sheets et al. and U.S. Pat. No. 4,981,081 to Summa are examples. All of these patents are directed to pusher dog variants that are designed to accomplish the movement of the aforementioned trolleys in a power and free conveyer system. However, references to pusher dogs or to conveyer systems that are adapted for operation without the use of trolleys are significantly less common. Some pusher dogs have been manufactured that were intended for use in conveyer systems that do not incorporate trolleys. Those pusher dogs were intended for use in conveyer systems wherein the pusher dogs were suspended from an upper rail or chain and were designed to engage hangers suspended on a series of interconnected rails disposed below the upper rail or chain. Those prior pusher dogs encountered several problems, including an unmanageable amount of friction between the pusher dogs and the series of interconnected rails, and difficulty in pushing hangers up inclined sections of the series of interconnected rails. In addition, prior pusher dogs were not reliably secured to the upper rail or chain. Under such, circumstances, the pusher dogs could not be maintained at a constant height above the series of interconnected rails and, thus, the aforementioned problem regarding friction between the pusher dogs and the series of interconnected rails was exacerbated.
Power and free overhead conveyer systems are often used in conjunction with high speed hanging garment sorters in the processing of GOH. In such an arrangement, GOH may be uploaded into a power and free system in the receiving area of a warehousing or distribution facility. The power and free system may then be used to transport single units or batches of GOH to the induction stations of the high speed garment sorters in a particular sequence or pattern. The high speed sorters are then used to separate the units or batches of GOH according to criteria such as size, style, color or shipment destination.
The use of power and free overhead conveyer systems that incorporate garment trolleys to move GOH has several disadvantages. High speed garment sorters have a potential throughput of at least 12,000 units per hour. Power and free systems cannot deliver GOH at a matching rate. The pusher dogs of power and free systems arc not designed to directly engage hangers on a system of tracks or rails. Instead, power and free pusher dogs engage trolleys that are, in turn, carrying loads of GOH. As a result, while power and free systems may be able transport up to 200 garments per minute past a given point, the garment trolleys must be manually offloaded before the GOH can be transferred to the high speed sorters, thus reducing the delivery rate drastically. Therefore, the use of power and free conveyer systems in conjunction with high speed sorters effectively starves the sorters and forces them to run below capacity. This represents an inefficient use of resources and reduces the overall productivity of facilities.
The garment trolleys themselves also present various difficulties. Trolleys represent an added expense for any facility, both in purchase and maintenance costs. Also, conveyer systems incorporating trolleys can be noisy to operate. Further, additional costs are often incurred by users of power and free systems since they must also install a return system for empty trolleys (i.e., so that the trolleys can be conveyed to their starting position once the garments have been manually transferred from the trolleys to the high speed sorters). Finally, the above-mentioned manual offload of garment trolleys from power and free systems is physically demanding and can result in personal injury. The low efficiency of power and free systems and the physically demanding aspect of their use results in high labor costs.
The existing art is therefore not sufficient for the task of moving large volumes of GOH or other products in a cost-effective and efficient manner. A suitable pusher dog for a high capacity conveyer system that does not incorporate trolleys is desired.